Variable valve actuation camshaft

Abstract

A camshaft assembly for variably actuating poppet valves of an internal combustion engine in relation to angular velocity. Pairs of cam lobes are separated by centripetal acceleration thereby varying dwell to optimize fuel economy, power output and emissions over a wide range of operating speeds.

What is claimed is: 
     
       1. A camshaft for an internal combustion engine, the camshaft rotates about a longitudinal axis, the camshaft includes a generally cylindrical exterior surface circumscribing the longitudinal axis as well as first and second axial end surfaces which are generally orthogonal to the longitudinal axis, the camshaft comprising: a passage extending parallel to the longitudinal axis;   a first pair of cams, at least a primary one of said first pair of cams is rotatably supported on the exterior surface, said primary one of said first pair of cams includes a first primary interior surface circumscribing and confronting said exterior surface, said primary one of said first pair of cams further includes a first primary groove in said first primary interior surface;   a second pair of cams, at least a primary one of said second pair of cams is rotatably supported on the exterior surface, said primary one of said second pair of cams includes a second primary interior surface circumscribing and confronting said exterior surface, said primary one of said second pair of cams further includes a second primary groove in said second primary interior surface;   an actuator rod extending in said passage, said actuator rod includes a first lateral projection engaging said first primary groove and a second lateral projection engaging said second primary groove; and   centrifugal means for causing displacement of said actuator rod parallel to the longitudinal axis as a consequence of changes in angular speed of the camshaft;   wherein changes in angular speed of the camshaft cause longitudinal displacement of said actuator rod with said first and second lateral projections, in turn the longitudinal displacement of said first and second lateral projections cause both said primary one of said first pair of cams and said primary one of said second pair of cams to rotate relative to the camshaft.   
     
     
       2. The camshaft according to claim 1, wherein said passage is centrally located so as to be coincident with the longitudinal axis. 
     
     
       3. The camshaft according to claim 2, further comprising: a plurality of apertures extending from said passage to the exterior surface of the camshaft, said apertures are elongated such that a majority component of said aperture extends along the longitudinal axis.   
     
     
       4. The camshaft according to claim 1, wherein said first primary groove and said second primary groove are helical. 
     
     
       5. The camshaft according to claim 4, further comprising: a plurality of apertures extending from said passage to the exterior surface of the camshaft, said apertures are elongated parallel to the longitudinal axis.   
     
     
       6. The camshaft according to claim 1, wherein said first primary groove and said second primary groove extend parallel with respect to the longitudinal axis, and said passage is centrally located so as to be coincident with the longitudinal axis. 
     
     
       7. The camshaft according to claim 6, further comprising: a plurality of apertures extending from said passage to the exterior surface of the camshaft, said apertures are helical shaped with respect to the longitudinal axis;   wherein said actuator rod is articulated such that relative angular orientation of said first and second lateral projections with respect to the longitudinal axis is variable.   
     
     
       8. The camshaft according to claim 1, further comprising: a secondary one of said first pair of cams; and   a secondary one of said second pair of cams;   wherein said secondary one of said first pair of cams and said secondary one of said second pair of cams are fixed with respect to the camshaft.   
     
     
       9. The camshaft according to claim 1, further comprising: a secondary one of said first pair of cams; and   a secondary one of said second pair of cams;   wherein said secondary one of said first pair of cams and said secondary one of said second pair of cams are rotatable with respect to said primary one of said first pair of cams and said primary one of said second pair of cams, respectively, as well as the camshaft.   
     
     
       10. The camshaft according to claim 9, further comprising: resilient means for angularly biasing said primary ones of said first and said second pairs of cams with respect to said secondary ones of said first and said second pairs of cams, respectively.   
     
     
       11. The camshaft according to claim 10, wherein said resilient means are arcuate shape springs having a first end attached to said primary ones of said first and said second pairs of cams, and a second end attached to said secondary ones of said first and said second pairs of cams. 
     
     
       12. The camshaft according to claim 1, further comprising: a drive gear fixed to said camshaft for concomitant rotation about the longitudinal axis, said drive gear including at least one radially elongated pocket;   wherein said centrifugal means include: a weight slidably disposed in each said at least one pocket, said weight having an oblique first face with respect to the longitudinal axis; and   an actuator element having a second face slidably engaging said first face, said actuator element is operatively connected to said actuator rod;   wherein changes in angular velocity of said drive gear cause radial displacement of said weight, in turn this causes longitudinal displacement of said actuator element and said actuator rod as a consequence of said first face sliding relative to said second face.     
     
     
       13. The camshaft according to claim 12, wherein said centrifugal means further includes resilient means for radially retracting said weight toward the longitudinal axis. 
     
     
       14. The camshaft according to claim 12, wherein said first face and said second face have the same oblique orientation with respect to the longitudinal axis such that said first and said second faces slide parallel with respect to one another. 
     
     
       15. The camshaft according to claim 12, wherein said first face and said second face are both obliquely oriented at 45° with respect to the longitudinal axis. 
     
     
       16. The camshaft according to claim 12, further comprising: a link connecting said actuator element and said actuator rod, said link is axially positioned between the first and second axial end surfaces;   wherein said actuator element is axially positioned between said link and said drive gear, said weight is axially positioned between said drive gear and said actuator element, and said drive gear is axially proximate to the first axial end surface.   
     
     
       17. The camshaft according to claim 16, wherein said passage is centrally located so as to be coincident with the longitudinal axis, and said link extends into said passage through at least one penetration in the exterior surface. 
     
     
       18. The camshaft according to claim 17, further comprising: return means for axially displacing said actuator rod toward the first axial end surface, said return means is axially proximate to the second axial end surface.